1. Field of the Invention
The subject matter of the present application relates to microelectronic packaging, and more specifically to multi-chip microelectronic memory packages, such as which include multiple dynamic random access memory (“DRAM”) chips in the same package.
2. Description of the Related Art
Microelectronic elements generally comprise a thin slab of a semiconductor material, such as silicon or gallium arsenide, commonly called a die or a semiconductor chip. Semiconductor chips are commonly provided as individual, packaged units in form of microelectronic packages. In some designs, the semiconductor chip is mounted to a substrate or chip carrier, which is in turn mounted on a circuit panel, such as a printed circuit board.
The active circuitry is fabricated in a first face of the semiconductor chip (e.g., a front face or surface). To facilitate electrical connection to the active circuitry, the chip is provided with bond pads on the same face. The bond pads are typically placed in a regular array either around the edges of the die or, for many memory chips, in the die center. The bond pads are generally made of a conductive metal, such as copper, or aluminum, around 0.5 micron (μm) thick. The bond pads could include a single layer or multiple layers of metal. The size of the bond pads will vary with the specific type of chip but will typically measure tens to hundreds of microns on a side.
Size is a significant consideration in any physical arrangement of chips. The demand for more compact physical arrangements of chips has become even more intense with the rapid progress of portable electronic devices. Merely by way of example, devices commonly referred to as “smart phones” and “tablet computers” integrate the functions of a cellular telephone with powerful data processors, memory and ancillary devices such as global positioning system receivers, electronic cameras, and local area network connections along with high-resolution displays and associated image processing chips. Such devices can provide capabilities such as full internet connectivity, entertainment including full-resolution video, navigation, electronic banking and more, all in a pocket-size device. Complex portable devices require packing numerous chips into a small space. Moreover, some of the chips have many input and output connections, commonly referred to as “I/O's.” These I/O's must be interconnected with the I/O's of other chips. The components which form the interconnections should not greatly increase the size of the assembly. Similar needs arise in other applications as, for example, in data servers such as those used in internet search engines. For example, structures which provide numerous short, interconnects between complex chips can increase the bandwidth of the search engine and reduce its power consumption.
In view of the foregoing, it can be advantageous to assemble multiple chips, particularly memory chips such as DRAMs in multi-chip memory packages. Further improvements can be made to the structure and function of multi-chip memory packages.